Technical Field
The present invention relates to a stator for a rotating electrical machine that is mounted in a vehicle or the like and used as an electric motor or a power generator.
Related Art
In related art, a rotating electrical machine that includes a rotor, a stator core, and a stator winding is generally known as a rotating electrical machine that is mounted and used in a vehicle. The rotor is provided in a rotatable manner. The stator core is disposed such as to oppose the rotor in a radial direction. The stator core has a plurality of slots that are arrayed in a circumferential direction. The stator winding is wound around the slots in the stator core.
JP-B-3899685 discloses a stator winding that is configured by a plurality of conductor segments that are each formed into a substantially U-shape. The terminals of the conductor segments are connected to one another. The stator winding is wound around a stator core by open end portions of the plurality of conductor segments being inserted into the slots from one axial-direction side. The open end portions extend towards the other axial-direction end side. The open end portions are then twisted in a circumferential direction, thereby forming oblique portions. The terminals of the oblique portions of differing conductor segments are joined with one another by welding or the like.
In addition, JP-B-3899685 discloses an insulating sheet member that is interposed between an inner wall surface of the slot and the conductor segment. The insulating sheet member is disposed in a state in which both axial-direction end portions project from the axial-direction end surface of the stator core, such as to set an allowance (creepage distance) from the axial-direction end surface of the stator core. This is to ensure electrical insulation (insulation to the earth) between the stator core and the stator winding.
As in the above-described stator disclosed in JP-B-3899685, the stator winding is formed by the plurality of conductor segments being joined together. In the stator winding, the open end portions extend from the slots toward the other axial-direction end side. A straight portion and the oblique portion are present at the base of the twist in the open end portion. The straight portion extends in the axial direction. The oblique portion slants in the circumferential direction from the tip of the straight portion. Therefore, to achieve size reduction by reducing the projection height of a coil end portion of the stator winding, the straight portions of the open end portions that extend from the slots are required to be made smaller. The coil end portion of the stator winding projects outward in the axial direction from the axial-direction end surface of the stator core. The straight portions extend in the axial direction.
However, in an instance in which the straight portion is made smaller, stretching stress applied to the end portion of the insulating sheet member that projects from the axial-direction end surface of the stator core increases, when the open end portion extending from the slot towards the other axial-direction end side is twisted in the circumferential direction. Therefore, tearing in the end portion of the insulating sheet member occurs more easily. When tearing occurs in the insulating sheet member in this way, the creepage distance becomes insufficient. The possibility of an insulation defect, such as creepage discharge, increases. Sufficient insulation cannot be ensured.